363
FXUS21 KWNC 122001
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 12 2025
SYNOPSIS: STRONG MID-LEVEL AND SURFACE LOW PRESSURE OVER THE NORTH PACIFIC
BRING THE POTENTIAL FOR A VARIETY OF HAZARDOUS WEATHER INCLUDING HIGH WINDS,
HEAVY PRECIPITATION, AND HIGH-ELEVATION SNOW ACROSS THE WESTERN CONTIGUOUS U.S.
(CONUS) THROUGHOUT THE WEEK-2 PERIOD. SURFACE LOW PRESSURE OVER THE GREAT
PLAINS ALONG WITH SURFACE HIGH PRESSURE OVER THE SOUTHEAST U.S. PAIR TO PRODUCE
POTENTIALLY HAZARDOUS WINDS OVER MUCH OF THE PLAINS, UPPER MISSISSIPPI VALLEY,
AND GREAT LAKES. STRONG SURFACE HIGH PRESSURE OVER THE YUKON IS FAVORED TO PUSH
EXTREMELY COLD AIR INTO SOUTHEASTERN ALASKA, POTENTIALLY BELOW HAZARDOUS
CRITERIA.
HAZARDS
MODERATE RISK OF HEAVY SNOW FOR THE CASCADES, KLAMATH, AND NORTHERN AND CENTRAL
SIERRA NEVADAS, SAT-FRI, DEC 20-26.
MODERATE RISK OF HEAVY SNOW FOR THE NORTHERN ROCKIES, SAT-FRI, DEC 20-26.
MODERATE RISK OF HEAVY SNOW FOR THE CENTRAL AND SOUTHERN ROCKIES, AND THE
WASATCH RANGE, MON-FRI, DEC 22-26.
SLIGHT RISK OF HEAVY SNOW FOR THE CASCADES, KLAMATH, AND SIERRA NEVADAS,
SAT-FRI, DEC 20-26.
SLIGHT RISK OF HEAVY SNOW FOR THE ROCKIES AND THE RANGES OF THE INTERMOUNTAIN
WEST, SAT-FRI, DEC 20-26.
MODERATE RISK OF HEAVY PRECIPITATION OF PORTIONS OF NORTHERN CALIFORNIA AND
COASTAL PORTIONS OF OREGON AND WASHINGTON, SAT-FRI, DEC 20-26.
MODERATE RISK OF HEAVY PRECIPITATION FOR COASTAL PORTIONS OF CENTRAL AND
SOUTHERN CALIFORNIA, MON-FRI, DEC 22-26.
SLIGHT RISK OF HEAVY PRECIPITATION ALONG THE ENTIRE WEST COAST, SAT-FRI, DEC
20-26.
MODERATE RISK OF HIGH WINDS FOR MUCH OF NORTHERN CALIFORNIA, THE PACIFIC
NORTHWEST, NORTHERN GREAT BASIN, AND NORTHERN ROCKIES, SAT-FRI, DEC 20-26.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF CALIFORNIA, PACIFIC NORTHWEST, GREAT
BASIN, NORTHERN ROCKIES, NORTHERN AND CENTRAL PLAINS, MIDDLE AND UPPER
MISSISSIPPI VALLEY, AND GREAT LAKES, SAT-FRI, DEC 20-26.
SLIGHT RISK OF HIGH WINDS FOR THE ALASKA PENINSULA, SOUTHERN MAINLAND ALASKA,
AND SOUTHEASTERN ALASKA, SAT-FRI, DEC 20-26.
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR SOUTHEASTERN ALASKA,
SAT-WED, DEC 20-24.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF SOUTH-CENTRAL AND
SOUTHEASTERN ALASKA, SAT-FRI, DEC 20-26.
FLOODING POSSIBLE FOR PORTIONS OF THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA.
DETAILED SUMMARY
FOR MONDAY DECEMBER 15 - FRIDAY DECEMBER 19:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY DECEMBER 20 - FRIDAY DECEMBER 26:
TODAY’S MODEL SOLUTIONS CONTINUE TO DEPICT WITH EXCELLENT AGREEMENT AN ACTIVE AN
D PERSISTENT SYNOPTIC PATTERN OVER THE NORTH PACIFIC AND WESTERN NORTH AMERICA.
THE 0Z ECMWF, GEFS, AND CANADIAN ENSEMBLES DEPICT AN AMPLIFIED MID-LEVEL RIDGE C
ENTERED OVER THE BERING SEA, WITH AN AMPLIFIED DOWNSTREAM MID-LEVEL TROUGH EXTEN
DING FROM THE NORTH PACIFIC ACROSS THE PACIFIC NORTHWEST AND INTO THE HIGH LATIT
UDES OF CANADA. AT THE SURFACE, THIS SET-UP FAVORS PERSISTENT HIGH PRESSURE ACRO
SS MUCH OF ALASKA AND THE YUKON THROUGHOUT WEEK-2. CONVERSELY, MEAN LOW PRESSURE
IS FAVORED IN THE GULF OF ALASKA. THE PRESSURE GRADIENT BETWEEN THESE FEATURES
BRINGS INCREASED CHANCES FOR EPISODES OF HIGH WINDS ACROSS MUCH OF SOUTHERN ALAS
KA FROM THE CENTRAL ALEUTIAN ISLANDS THROUGH SOUTHEAST ALASKA. HIGH WINDS WOULD
BE PARTICULARLY FAVORED IN GAPS AND INLETS. PROBABILISTIC EXTREMES TOOLS (PETS)
SHOW ENHANCED CHANCES OF WIND SPEEDS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTIL
E. THEREFORE, A SLIGHT RISK OF HIGH WINDS IS POSTED FOR MOST OF SOUTHERN AND SOU
THEASTERN ALASKA FOR ALL OF WEEK-2.
PETS CONTINUE TO HIGHLIGHT ENHANCED CHANC
ES FOR TEMPERATURES TO FALL TO NEAR HAZARDOUS THRESHOLDS ACROSS PORTIONS OF SOUT
H-CENTRAL, INTERIOR, AND SOUTHEAST ALASKA. AS THE BERING SEA RIDGE SLOWLY WEAKEN
S, THE ANOMALOUS COLD (AND ASSOCIATED NORTHERLY FLOW) WILL GRADUALLY EXPAND WEST
WARD ACROSS THE STATE. A MODERATE RISK IS POSTED FOR SOUTHEAST ALASKA FOR DEC 20
-24, WHILE A BROADER SLIGHT RISK IS MAINTAINED FOR MUCH OF SOUTH-CENTRAL AND SOU
THEAST ALASKA FOR ALL OF WEEK-2. TEMPERATURES BETWEEN -20 DEG F AND -35 DEG F AR
E PREDICTED TO BE WIDESPREAD ACROSS MUCH OF INLAND ALASKA, WITH -40 DEG F TEMPER
ATURES INDICATED BY THE PETS OVER THE EASTERN INTERIOR TO THE NORTH OF FAIRBANKS
. CLOSER TO THE COAST, TEMPERATURES ARE EXPECTED TO RANGE BETWEEN 0 AND -15 DEG
F (ANCHORAGE NEAR -10 DEG F), WHILE THE SOUTHERN HALF OF SOUTHEAST ALASKA IS PRE
DICTED TO BE SOMEWHAT MILDER, WITH HIGH TEMPERATURES ABOUT +10 DEG F. THE COMBIN
ATION OF VERY COLD WEATHER AND HIGH WINDS ALONG THE SOUTHERN TIER OF THE STATE I
NCREASES THE THREAT FOR HEAVY FREEZING SPRAY AT TIMES NEAR LARGER BODIES OF WATE
R.
THE 0Z ECENS, 0Z GEFS, AND 0Z CMCE MODEL SOLUTIONS DEPICT PERSISTENT MID-L
EVEL TROUGHING OVER THE NORTH PACIFIC AND BROAD POSITIVE 500-HPA HEIGHT ANOMALIE
S ACROSS MUCH OF THE SOUTHERN CONUS, RESULTING IN AN ENHANCED JET STREAM OVER TH
E PACIFIC NORTHWEST. THE INTEGRATED VAPOR TRANSPORT (IVT) TOOL ALSO INDICATES DE
EP LOW-LEVEL MOISTURE STREAMING INTO THE WEST COAST THROUGHOUT THE FORECAST PERI
OD, WITH BOTH THE ECMWF AND GEFS SHOWING PROBABILITIES EXCEEDING 40% FOR IVT TO
EXCEED 250 KG/M/S. THE PETS AND UNCALIBRATED PRECIPITATION GUIDANCE SUPPORTS A S
LIGHT RISK OF HEAVY PRECIPITATION ALONG THE ENTIRE WEST COAST FOR ALL OF WEEK-2.
A MODERATE RISK FOR HEAVY PRECIPITATION IS INDICATED FOR THE PACIFIC NORTHWEST,
NORTHERN AND PORTIONS OF CENTRAL CALIFORNIA, ALSO FOR ALL OF WEEK-2. PRECIPITAT
ION AMOUNTS OF 2 INCHES ARE PREDICTED BY PET GUIDANCE WITHIN THIS BROAD REGION O
F ELEVATED ONSHORE FLOW FROM WASHINGTON STATE SOUTHWARD TO CENTRAL CALIFORNIA. B
OTH THE GEFS AND ECMWF INDICATE AR ACTIVITY TO SHIFT FURTHER SOUTH BY THE MIDDLE
OF WEEK-2, AND THE POTENTIAL FOR HEAVY PRECIPITATION WITH IT, THEREFORE A MODER
ATE RISK OF HEAVY PRECIPITATION IS POSTED FOR COASTAL PORTIONS OF CENTRAL AND SO
UTHERN CALIFORNIA FOR DEC 22-26. THIS FORECASTED HEAVY PRECIPITATION, IN ADDITIO
N TO THE ANTECEDENT WEEK-1 PRECIPITATION, IS LIKELY TO AGGRAVATE FLOODING ISSUES
FOR THE PACIFIC NORTHWEST, WITH A FLOODING POSSIBLE HAZARD REMAINING POSTED AND
EXTENDED INTO NORTHWESTERN CALIFORNIA. CONTINUED PRECIPITATION ACCUMULATIONS ON
SATURATED SOILS BRINGS THE ADDITIONAL RISKS OF LANDSLIDES AND DEBRIS FLOWS IN S
TEEP TERRAIN OR BURN SCARS, AS WELL AS THE POTENTIAL FOR URBAN AND FLASH FLOODIN
G ACROSS THE REGION.
THE INCOMING MOISTURE ASSOCIATED WITH THIS ATMOSPHERIC R
IVER IS LIKELY TO PUSH WELL INLAND, RESULTING IN POTENTIALLY HEAVY SNOW FOR MANY
MOUNTAIN RANGES ACROSS THE WEST. UNCALIBRATED PROBABILITIES FROM BOTH THE ECENS
AND GEFS FOR DAILY ACCUMULATIONS OF OVER 6 INCHES EXCEED 40% IN SOME LOCATIONS
THROUGHOUT THE WEEK, AND THE GEFS PET FOR SNOW WATER EQUIVALENT (SWE) INDICATES
AT LEAST A 20% CHANCE OF 3-DAY SWE TO EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE
AND AT LEAST 1 INCH FOR MUCH OF THE CASCADES, SIERRAS, AND NORTHERN AND CENTRAL
ROCKIES THROUGHOUT THE WEEK. BASED ON THE GEFS PET AND UNCALIBRATED DAILY SNOWFA
LL TOTALS, A MODERATE RISK OF HEAVY SNOW FOR ALL OF WEEK-2 FOR THE CASCADES, KLA
MATH, AND NORTHERN AND CENTRAL SIERRAS, AND A SLIGHT RISK OF HEAVY SNOW EXTENDIN
G OVER THE SOUTHERN SIERRAS, ALSO FOR THE WHOLE WEEK. FURTHER EAST, A BROAD AREA
ENCOMPASSING MOST OF THE ROCKIES AND RANGES OF THE INTERMOUNTAIN WEST IS INDICA
TED FOR A SLIGHT RISK OF HEAVY SNOW THROUGHOUT THE FORECAST PERIOD. ADDITIONALLY
, A MODERATE RISK IS POSTED FOR THE NORTHERN ROCKIES FOR ALL OF WEEK-2, AS WELL
AS A MODERATE RISK OF HEAVY SNOW FOR THE WASATCH, AND THE CENTRAL AND SOUTHERN R
OCKIES, COVERING THE PERIOD DEC 22-26.
ALONG WITH HEAVY PRECIPITATION AND SNO
W, HIGH WINDS REACHING HAZARDOUS CRITERIA ARE ALSO POSSIBLE ASSOCIATED WITH THIS
ATMOSPHERIC RIVER (AR) EVENT. THIS IS WELL INDICATED BY THE ECMWF AND GEFS PETS
WHICH INDICATE AT LEAST A 20% CHANCE OF 3-DAY MAXIMUM WIND SPEEDS EXCEEDING THE
85TH PERCENTILE FOR MUCH OF THE CONUS THROUGHOUT THE WEEK. OVER THE WESTERN CON
US, ENHANCED WINDS ARE LIKELY THE RESULT OF DEEP TROUGHING AND AR OVER THE WEST
COAST, WHILE PERIODS OF SURFACE LOW PRESSURE OVER THE PLAINS AND HIGH PRESSURE O
VER THE SOUTHEAST U.S. ARE THE FEATURES ENHANCING WINDS ELSEWHERE. A SLIGHT RISK
OF HIGH WINDS IS POSTED FOR MOST OF THE WESTERN CONUS AS WELL AS THE NORTHERN A
ND CENTRAL PLAINS AND GREAT LAKES REGIONS FOR ALL OF WEEK-2. THE ECMWF PET IS ES
PECIALLY BULLISH, WITH PROBABILITIES EXCEEDING 80% FOR MUCH OF THE NORTHWESTERN
CONUS EARLY IN WEEK-2, FURTHER BACKED BY PATTERN RECOGNITION, WARRANTING A MODER
ATE RISK OF HIGH WINDS FOR MUCH OF THE PACIFIC NORTHWEST, NORTHERN GREAT BASIN,
AND NORTHERN ROCKIES, ALSO FOR THE WHOLE FORECAST PERIOD.
FORECASTER: DANNY BAR
ANDIARAN
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